A content server receives live streams from a content distributor to transmit to users of the content server. In one embodiment, the content server promotes the live streams received from the content distributor, by serving portions of the live stream as advertisements (ads) to users of the content server along with videos or digital content requested by the users. The content server buffers the live stream. The content server receives a request for a video from a client device. The content server identifies the video requested by the user and metadata associated with the identified video. The content server, based on the metadata determines whether to serve the client device with a live-stream ad, as a pre-roll ad for example, along with the video requested by the user. The content server then identifies a buffered live-stream ad to transmit to the client device along with the requested video.